1. Field of the Invention
The invention in general relates to hydrophones, and in particular to a low frequency dipole hydrophone which is inertia balanced.
2. Description of the Prior Art
Dipole hydrophones are used in the underwater environment for listening to very low frequency noise as may be produced by a submarine, for example.
The dipole hydrophone is positioned at some point in the water, either alone or as part of an array, and provides an output signal in response to received acoustic energy, in accordance with its beam pattern, in the form of a figure 8.
Most dipole hydrophones respond directly to particle velocity and any mechanical vibration acceleration from the support structure may tend to provide an unwanted output signal.
In copending application Ser. No. 352,820, filed Apr. 19, 1973, and assigned to the same assignee as the present invention, there is described an acceleration cancelling hydrophone which utilizes two masses having different ratios of actual mass to added mass with each being connected by means of a multilaminar magnetostrictive arm to a base member with the unit including first and second pickups for providing an output signal.
The present invention eliminates the need for two matched multilaminar arms, and eliminates the requirement of two matched pickup units.